Yes, why not? But i think you are looking for your answer in wrong place. Your friend which working in Japan must to go British Embassy and ask to them for take a visa.

 http://ukinjapan.fco.gov.uk/en/visas/

Here is the British Consulate website in Japan.  I can only assume he/she would have to apply here but the UK Borders Agency are getting very tough on non-EU and non- EAA entrants to the UK so don´t expect it to be easy to get a holiday visa for your Turkish friend.

thanks for the info

Surely it´s the passport you hold that determines the visa you get - not the country you are currently living in?  Therefore a Turkish person would find it no easier to get to Britain from Japan than from Turkey. 

 That is correct and now we have toughened entry to the UK, it will be even harder.  The British Consulate should be able to guide them, but I would hold out no hope whatsoever in getting a visa, and coming to the UK from outside Turkey.

 I agree